In the past, a motivation for deploying multimode fibre was its cheaper cost by comparison with single mode fibre. Unfortunately, multimode fibre has disadvantages over single mode fibre. In particular, signals traversing a multimode fibre will be dispersed or separated into a number of modes. Unfortunately, depending on the length of the multimode fibre, each mode may arrive at the destination at slightly different times. A receiver should compensate for this. Furthermore, the receiver should compensate for ISI (Inter-Symbol Interference) found in the received signal.
Recovering data received over a multimode fibre is accomplished using appropriate timing recovery. Many existing timing recovery circuits use a PLL (Phase Lock loop) to determine a proper sampling point. However, as data rates increase, existing timing recovery circuits are no longer adequate for properly recovering data received over multimode fibre. Adaptive equalization with appropriate timing recovery circuits can be used. An entire study group during the 802.3aq standard was involved in characterizing this problem.
Adaptive equalization can be an effective approach for recovering data received over multimode fibre. Additionally, adaptive equalization can be an effective approach for recovering data received over other types of communication channels such as long connections of a PCB (Printed Circuit Board) for example.